One patient had conjunctivitis in one eye, and the other had longer-lasting flulike symptoms.
In related developments, Colorado's governor recently extended an emergency declaration that frees up more resources to battle the outbreaks.
Nipah virus, which has a high fatality rate, is a top target for countermeasure development.
The girl's illness marks Cambodia's ninth H5N1 case of the year.
The latest confirmations also include more wild birds and small mammals from Weld County, a Colorado hit hard by dairy cow and poultry outbreaks.
Cattle herds in Colorado and South Dakota are the latest to be infected in the H5N1 avian flu outbreak.
The investigators also cultured infectious H5N1 virus from milk and cattle samples taken from 2 Texas dairy farms.
The CDC is offering support for targeted programs and vaccine supplies to states, part of a plan to cut the risk of H5N1 reassortment with seasonal flu.
So far, humans who have been infected with H5N1 via contact with infected cows have also exhibited mild illness.
Michigan's outbreak in dairy cows is its second of the month and is the first in Van Buren County.
